Drafting device

ABSTRACT

A drafting device for drawing ellipses, spirals and other complex figures is disclosed. The drafting device has a substantially vertical shaft with a writing point at the lower end thereof, and the apparatus required to draw the complex figures is contained substantially within the vertical shaft. Separate ellipse-forming and spiral-forming strings are drawable from the interior of the vertical shaft, and can be used in combination with pins or thumb tacks to draw a variety of complex shapes.

United States Patent Farmos July 16, 1974 [5 DRAFTING DEVICE 3,479,742 11/1969 Starkenberg 33/27 R [76] Inventor: George T. Farmos, 2207 Carroll St.,

. Prtmary Examzner-L0u1s R. Prince Oakland Cahf' 94606 Assistant Examiner-Charles E. Phillips [22] F11ed: Nov. 10, 1972 Attorney, Agent, or Firm-Townsend and Townsend [21] Appl No.: 305,622

[57] ABSTRACT, A drafting device for drawing ellipses, spirals and [52] US. Cl 33/30 E, 33/27 M other complex figures is disclosed The drafting device [51] lnt.Cl B43| l1/04,B431 11/06 h b ta n l h ft t t 5st Field of Search mm c, 27 M, 30 E, 13s s 5 a awmng a the lower end thereof, and the apparatus required to draw the complex figures is contained substantially (56] g gg z g Cited within the vertical shaft. Separate ellipse-forming and S PATENTS spiral-forming strings are drawable from the interior of 310,840 l/1885 Millner 33/138 X the vertical shaft, and can be used in combination with 32 3 pins or thumb tacks to draw a variety of complex ogs on e a 2,650,429 9/1953 Debs 33/30 E Shapes 2,800,717 7/1957 Debs 33/27 C 8 Claims, 7 Drawing Figures PATENTEDJUL 1 5 ran SiiiET 1 BF 2 J gw/ f C H MWMWWM J 5 Q PATENTED l I 6 74 SHEET 2 0F 2 1 DRAFTING DEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to drafting devices, and in particular to hand-held drafting devices for accurately drawing ellipses and other figures.

2. Description of the Prior Art The practice of drawing ellipses by means of a pencil in contact with a string wrapped around two pins has been known for a long time and is based on the mathematical formulation of ellipse. An early patent to Hanlon, U.S. Pat. No. 758,314, ELLIPSOGRAPH," contains the basic essentials of the system; a pencil, a string, and two pins. However, this simple system had the disadvantage that the string must be tied precisely to obtain the proper ellipse. This greatlyrestricted the actual use of the Ellipsograph by a draftsman, and led to attempts to improve on the Hanlon concept by providing a means of accurately adjusting the length of the string.

Patents were issued to Caldwell, U.S. Pat. No. l,230,994, MEANS FOR DESCRIBING CIRCULAR AND ELLIPTIC ARCS, and to Debs, U.S. Pat. No. 2,800,717, DRAFING INSTRUMENT. Caldwell provided a means for adjusting the string connected to one of the pins,.and Debs provided a means for adjusting the string connected to the pencil. These devices provided for accurate adjustment of the string, but led to other problemsIn the Caldwell device, the pencil point was not coincident with the connection to the string, and a waggling motion was inherent in the movement of the device in attempting to draw the ellipse, thus reducing the quality of the ellipse. The size of the device, which was positioned interior to the ellipse, prevented the drawing of ellipses with small semi-minor axes since the device could notpass by the pins. The

Debs device had the same problem of waggling associated with the Caldwell device, and provided the added difficulty of independently moving the drafting ing work. All of the equipment needed to draw the ellipse or' other complex figure is included within the drafting instrument itself with the exception of the pins.

The procedure for drawing an ellipse with the present device is simple. A button is depressed to allow string to be pulled from the interior of the pencil. When the proper amount of string is measured, a second button is depressed to lock the string in position. The string mechanism is contained within a rotatable housing within the drafting device itself, and the ellipse can be fully formed by moving the drafting device as delimited by the string. After the ellipse is completed, the first button is depressed and the string is drawn back inside the drafting device by a spring-loaded reel. As an added feature, a second string is contained within the drafting device and can be used to form spiral figures.

SUMMARY OF THE INVENTION The invention relates to a drafting device having a substantially vertical shaft with a writing point positioned at the lower end of the vertical shaft.- An ellipseforming string is storable within the vertical shaft and is drawable outside the vertical shaft, and means are provided for delimiting the drawing of the ellipseforming-string outside the vertical shaft.

The novel features which arebelieved to be characteristic of the invention, both as to organization and method of operation, together with further objects and advantages thereof will be better understoodfrom the following description considered inconnection with the accompanying drawings. in whichga preferred. em-

instrument at the same time as the penciLBoth the Caldwell and Debs devices did not have an integral writing point but required the addition of. the writing instrument itself, and the writing instrument hadto fit the attachment mechanism, v The difficulties involved in drawing ellipses sufficiently accurately for drafting work led to the development of more and more complex devices. Examples of such devices are illustrated in the patent to Barker, U.S. Pat. No. 2,831,251, ELLIPSOGRAPH, and the patent toTerrell, U.S. Pat. No. 3,224,098,.ELLIPSE SCRIBER. These devices are extremely complex, making them too expensive for most draftsmen, and are so specialized that they may only be usedfor drawing ellipses within a limited size range. The complexity of the machinery also tends to get in the way of the drawing of the ellipse itself, such as in the Terrell device, where the armature prevents the drawing of the full ellipse in a single motion and the instrument must be lifted and moved to complete the ellipse. I The present invention illustf'zfies'a deviee which, while utilizing the basic ellipse-drawing principal of a string and two pins, presents a simple devicefor the drawing of accurate ellipses. The device is also applicable to drawing shapes other than ellipses, and is readily useable as a standard drafting pencil for normal draftbodiment of the inventionis'illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intendedas a definition of thelimits of the invention. i

' BRIEF DESCRIPTION oF Tl-IEDRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT The interior construction of the drafting device is illustrated in the side cross-sectional view of FIG. 1. The I drafting device 10 has a vertical shaft 11 with a writing point 12 positioned at the lower end of the vertical shaft. The writing point may consist of a pencil point, ball-point pen, or other writing instrument. An ellipseforming string 13 is partially wound on a reel 14 contained in a rotatable housing 15.'The housing 15 is located substantially within the vertical shaft 11, but is in communication with the exterior of the vertical shaft by means of a small hole 16 on the exterior of the hous- FIG. 4 illustrates a circle drawn by the drafting deing. One end of the ellipse-forming string 13 passes through the hole 16 in the housing and is attached to the exterior of the housing adjacent the hole.

The reel 14 containing the ellipse-forming string 13 is rotatable with respect to the housing 15. In this manner, the ellipse-forming string 13 can be drawn out of the housing 15 when an ellipse is to be formed. As the ellipse-forming string 13 is drawn out of the housing 15, a spring 17 is tensioned whereby the reel 14 is biased to take up the ellipse-forming string 13. When the desired amount of ellipse-forming string 13 has been drawn out of the housing 15 for proper formation of the ellipse, the position of the reel 14 relative to the housing 15 is locked to prevent further removal of the ellipse-forming string 13. The locking is accomplished by a pin 18 which meshes with sprocket teeth 19 disposed on the periphery of the reel 14 and corresponding sprocket teeth 20 disposed on the interior surface of the housing 15. The correspondence of the sprocket teeth is more fully illustrated by reference to FIG. 2, taken along line 2-2 of FIG. 1. Sprocket teeth 19 are illustrated disposed about the periphery of the reel 14, and corresponding sprocket teeth 20 are disposed about the interior surface of the housing 15. The pin 18 is adapted to mesh with the corresponding sprocket teeth to prevent rotation of the reel 14 relative to the housing 15.

Referring back to FIG. 1, the method by which the pin 18 is meshed with the sprocket teeth 19 disposed about the periphery of the reel 14 and the sprocket teeth 20 disposed about the interior surface of the housing 15 is illustrated. The pin 18 is mounted on a rotatable U-shaped channel member 21. A shaft 22 con nected to a button 23 mates with the U-shaped channel member 21 and is adapted to press down on the U- shaped channel to mesh the pin 18 in position. The button 23 is biased to the position illustrated wherein it does not interfere with the rotation of the housing 15 by means of a spring 24. A corresponding shaft 25 attached to a button 26 also mates with the U-shaped channel member 21 and isadapted to unmesh the pin 18. A linkage composed of members 27 and 28 connect the button 26 with shaft 25in such a manner that the shaft 25 is raised and thereby raises the U-shaped channel member 21 when the button 26 is depressed. The button 26 is biased to the position illustrated in which it does not interfere with the rotation of the housing 15 by means of a spring 29.

The entire housing 15 which contains the reel 14 is rotatable about the longitudinal axis of the vertical shaft 11. In this manner, the attachment point of the ellipse-forming string 13 with the drafting device 10 is freely rotatable about the drafting device so that irrotational motion of the vertical shaft 11 during the construction of the ellipse does not interfere with the quality of the ellipse. The buttons 23 and 26 which mesh and unmesh the pin 18 are specifically designed so that there is no contact, frictional or otherwise, with the rotational housing which would interferewith the proper construction of the ellipse.

Referring still to FIG. 1, 'a spiral-forming string 30 partially wound on a circular ring 31 having a central axis coincident with the longitudinal axis of the vertical shaft 11 is illustrated. Ring 31 is non-rotatably attached to shaft 11. The spiral-forming string 30 passes through a small hole 32 on an external ring 33 which is rotatable about the longitudinal axis of the vertical shaft 11. The

4 spiral-forming string has a knot 34 on the end thereof to prevent the entire string from being drawn inside the external ring 33. The knotted end 34 of the spiralforming string 30 can be attached to a pin (not shown), and the spiral is formed by moving the drafting device 10 irrotationally around the pin while keeping constant tension on the spiral-forming string 30 whereby the spiral-forming string is unwound from the circular ring 30, thus increasing the length of the spiral-forming string available and forming the spiral.

The operation of the drafting device 10 in drawing an ellipse 41 is illustrated by reference to FIG. 3. The ellipse-forming string 13 is drawn out of the drafting device 10 to form a closed loop as illustrated. The string is wrapped around two pins 42 and 43, and the drafting device 10 is tensioned against the ellipse-forming string 13 to form the ellipse.

Use of the drafting device 10 to form a circle 44 is illustrated in FIG. 4. A circle can be considered as an ellipse having coincident foci, hence it is obvious that the ellipse-forming string 13 can be used with a single pin 45 to form the circle.

FIG. 5 illustrates the drafting device 10 used to form a spiral 46. The spiral-forming string 30 is attached to a single pin 47, and the spiral is formed by irrotationally moving the drafting device 10 about the end of the spiral-forming string 30.

FIG. 6 illustrates the drafting device 10 used to form an oblate spiral 48. Theoblate spiral is formed by wrapping the spiral-forming string 30 around two pins 49 and 50, and then unwrapping the string by moving the drafting device 10 irrotationally about the end of the string.

FIG. 7 illustrates the drafting device 10 used to form an egg-shaped figure 51, and illustrates how the drafting device may be used to form various shaped figures by using different numbers and arrangements of pins. In FIG. 7, the ellipse-forming string 1.4 is wrapped around three pins 52, 53 and 54 to form the egg-shaped figure 51.

What is claimed is:

l. A drafting device comprising: a substantiallyvertical shaft having a writing point positioned at the lower end thereof; a housing located substantially within the vertical shaft in communication with the exterior thereof, said housing rotatable about the longitudinal axis of said vertical shaft; a reel mounted in the housing and rotatable with respect thereto; an ellipse-forming string windableon the reel and withdrawable outside the housing; and means for selectively preventing rotation of the reel relative to the housing to control with drawal of the ellipse-forming string outside the housing.

2. A device as recited in claim 1 wherein the reel is rotatable about the longitudinal axis of the vertical shaft.

3. A device as recited in claim 1 wherein the means for selectively preventing rotation of the reel relative to the housing comprises correspondingly juxtaposed sprocket teeth disposed about the periphery of the reel and about the interior surface of the housing, and a pin mesha'ble with the sprocket teeth to prevent rotation of the reel relative to the housing.

4. A device as recited in claim 3 and additionally comprising a rotatable U-shaped channel member attached to the pin, a first spring-biased button engagable with the U-shaped channel member so that said U- shaped channel member is depressed when said first spring-biased button is depressed to mesh the pin with the sprocket teeth, and a second spring-biased button engagable with the U-shaped channel member so that said U-shaped channel member is raised when said second spring biased button is depressed to unmesh the pin from the sprocket teeth.

5. A drafting device comprising: a substantially vertical shaft having a writing point positioned at the lower end thereof; an ellipse-forming string storable within the vertical shaft and withdrawable outside the vertical shaft; means for selectively controlling the withdrawal of the ellipse-forming string outside the vertical shaft; and a spiral-forming string windable on a circular ring located within the vertical shaft such that said spiralforming string is withdrawable from the interior of said vertical shaft upon rotation of said vertical shaft.

6. A drafting device comprising:

an elongate handle adapted to be generally held in a vertical position and having a rotatable portion having a small hole on the outer wall of the rotatable portion providing an opening to the interior of the handle;

a writing point at the lower end of the handle;

a string storable within the handle and withdrawable through the hole in the rotatable portion, said string having one end attached to the rotatable portion; take up means within the handle adapted to draw the withdrawn string back within the handle, said take up means being attached to the rotatable portion of said handle; and

locking means selectively preventing withdrawal or take up of said string;

whereby string may be drawn from within the handle to form a loop of selected size, the loop of string used to draw a geometric figure such as an ellipse, and the withdrawn string drawn back into the handle so that the device can be used as a standard writing instrument.

7. A device as recited in claim 6 wherein the take up means comprises resilient means, said resilient means tensioned as the string is withdrawn so that said resilient means tends to draw the withdrawn string back within the shaft.

8. A device as recited in claim 6 and additionally comprising means providing an exposed section of string intermediate the attachment of said one end of said string and the hole to facilitate initial withdrawal of said string through said hole. 

1. A drafting device comprising: a substantially vertical shaft having a writing point positioned at the lower end thereof; a housing located substantially within the vertical shaft in communication with the exterior thereof, said housing rotatable about the longitudinal axis of said vertical shaft; a reel mounted in the housing and rotatable with respect thereto; an ellipse-forming string windable on the reel and withdrawable outside the housing; and means for selectively preventing rotation of the reel relative to the housing to control withdrawal of the ellipse-forming string outside the housing.
 2. A device as recited in claim 1 wherein the reel is rotatable about the longitudinal axis of the vertical shaft.
 3. A device as recited in claim 1 wherein the means for selectively preventing rotation of the reel relative to the housing comprises correspondingly juxtaposed sprocket teeth disposed about the periphery of the reel and about the interior surface of the housing, and a pin meshable with the sprocket teeth to prevent rotation of the reel relative to the housing.
 4. A device as recited in claim 3 and additionally comprising a rotatable U-shaped channel member attached to the pin, a first spring-biased button engagable with the U-shaped channel member so that said U-shaped channel member is depressed when said first spring-biased button is depressed to mesh the pin with the sprocket teeth, and a second spring-biased button engagable with the U-shaped channel member so that said U-shaped channel member is raised when said second spring biased button is depressed to unmesh the pin from the sprocket teeth.
 5. A drafting device comprising: a substantially vertical shaft having a writing point positioned at the lower end thereof; an ellipse-forming string storable within the vertical shaft and withdrawable outside the vertical shaft; means for selectively controlling the withdrawal of the ellipse-forming string outside the vertical shaft; and a spiral-forming string windable on a circular ring located within the vertical shaft such that said spiral-forming string is withdrawable from the interior of said vertical shaft upon rotation of said vertical shaft.
 6. A drafting device comprising: an elongate handle adapted to be generally held in a vertical position and having a rotatable portion having a small hole on the outer wall of the rotatable portion providing an opening to the interior of the handle; a writing point at the lower end of the handle; a string storable within the handle and withdrawable through the hole in the rotatable portion, said string having one end attached to the rotatable portion; take up means within the handle adapted to draw the withdrawn string back within the handle, said take up means being attached to the rotatable portion of said handle; and locking means selectively prevenTing withdrawal or take up of said string; whereby string may be drawn from within the handle to form a loop of selected size, the loop of string used to draw a geometric figure such as an ellipse, and the withdrawn string drawn back into the handle so that the device can be used as a standard writing instrument.
 7. A device as recited in claim 6 wherein the take up means comprises resilient means, said resilient means tensioned as the string is withdrawn so that said resilient means tends to draw the withdrawn string back within the shaft.
 8. A device as recited in claim 6 and additionally comprising means providing an exposed section of string intermediate the attachment of said one end of said string and the hole to facilitate initial withdrawal of said string through said hole. 